i did the clothes pin method, I did it many times and many more as i could not belive the results,  it used to be 29.5 so thats what ive been asuming for a few years, well now its 30 and 5/8.  im only six two but have a six eight wingspan.  bob w if you read this what is your wingspan and draw if i remember right its pretty long.

Puttin' the back into it more?

little of that and hand extension bow shoulder strength id imagine.  i used to pull that far when shooting ultra light longbow and when shooting my best ever.